It has become increasingly important in resin coating applications that curing of resin systems be accomplished at ambient temperatures and with little or no formation of volatile material.
Resilient seamless flooring is a recent innovation, having been developed during the last decade. A basic seamless floor is composed of a single continuous layer or coat of thermosetting plastic which is firmly bonded to a desired substrate. Seamless chip flooring is a relatively new concept in resilient seamless flooring and involves the on-site encasement of decorative chips in a clear, liquid plastic matrix.
The total number of coats and the thickness of each coat of thermosetting plastic applied to any given substrate depend in part upon the nature of the substrate, the composition of the thermosetting plastic, the method of application, and the properties or characteristics desired in the finished floor. Generally, any resilient seamless floor is comprised of a base coat and optionally one or more finish coats. A seamless chip floor usually consists of a base coat, an optional chip coat, decorative chips, one or more glaze coats, and one or more finish coats.
Because the color and pattern of a seamless floor are determined by the base coat and decorative chips, if used, the glaze and finish coats are clear. Obviously, any discoloration of the base coat resin will alter the color of the floor, especially with lightly-colored floors. Discoloration of the glaze and/or finish coats not only will alter the color of the floor, but also will mask the effect of decorative chips, if employed. Thus it is imperative that the resins employed for the base, glaze, and finish coats be free from discoloration from any cause, either before or during curing. Freedom from discoloration also is important when glaze coat resins are applied to walls and other surfaces as protective coatings.
Epoxy resins are among the materials which have been employed successfully as base coats and glaze coats, particularly the epoxy resins based on glycidyl ethers. Such resins, when cured with aliphatic amines, possess an outstanding number of advantages such as excellent adhesion to concrete, plywood, brick, ceramic tile, and plastic tile, resistance to bleedthrough, moisture resistance, low odor, flexibility (resilience), and low temperature curability.
Although listed above as an advantage of glycidyl ethers cured with aliphatic amines, low temperature curability in reality is a requirement of any resin intended for use in seamless flooring. This requirement stems from the rather obvious fact that it is wholly impractical to heat the resin onceapplied to the substrate. Thus any applied resin must cure at ambient temperature, which may be as low as about 40 degrees Fahrenheit.
In general, glycidyl ethers may be cured at ambient temperature by aliphatic amines. The lower the ambient temperature, however, the longer is the time required to cure the resin. It therefore is desirable to utilize an accelerator to keep cure times within reasonable limits.
Various classes of compounds are known to be accelerators for aliphatic amine/glycidyl ether systems. All, however, suffer disadvantages. For example, as a consequence of very pronounced temperature dependence, aliphatic and aromatic organic acids and aliphatic tertiary amines result in a short working life (pot life) and a very long film cure time. Aliphatic and aromatic mercaptans impart excessive and usually intolerable odor to the resin system. And sulfonamides and phenols discolor the resin system. The discoloration by phenols, the most commonly used accelerator class, is most pronounced with phenol itself, with less color being developed with such substituted phenols as nonylphenol. Hence, there is a need for novel accelerators and crosslinking agents for amine-curable epoxy resins.
Other resin coating systems which are of interest and which are being actively investigated are low viscosity thermoplastic compositions which are easily sprayed or cast onto substrates and which cure at ambient temperatures to highly crosslinked thermoset coatings substantially without evolution of volitile component. Essentially 100% of the low viscosity resin coating system is incorporated in the resultant thermoset coating.
It is therefore an object of the present invention to provide novel low temperature curable thermoplastic resin compositions which convert to highly crosslinked coating systems substantially without evolution of volitile material.
It is another object of the present invention to provide curable compositions derived from amine-containing resin compositions.
It is still another object of the present invention to provide novel accelerators and crosslinking agents for amine-modified epoxy resins, and for polyamino-polyaryl-polymethylene resins.